The present invention overcomes the shortcomings of the background art and provides sulfonated aromatic copolyetheresters containing hydroxyalkanoic acids with improved thermal properties, such as crystalline melting points, glass transition temperatures, and heat deflection temperatures, as compared to comparable art sulfonated aromatic copolyetheresters that contain hydroxyalkanoic acids.
Copolyesters of poly(hydroxyalkanoates) with aromatic dicarboxylic acids are known. For example, Gordon et al., in WO 91/02015, disclose hydrodegradable aliphatic-aromatic copolyesters that may include hydroxy acids. Imamura et al., in U.S. Pat. No. 5,605,981 and U.S. Pat. No. 5,616,657, disclose a process for the preparation of certain lactic acid copolyesters comprising 50–98 wt. % lactide. Warzelhan et al., in U.S. Pat. No. 5,817,721; U.S. Pat. No. 5,889,135; U.S. Pat. No. 6,018,004; and U.S. Pat. No. 6,303,677, disclose certain aliphatic-aromatic copolyesters containing hydroxy acids. Buchanan et al., in U.S. Pat. No. 6,342,304, disclose oriented films derived from linear aliphatic-aromatic copolyesters prepared from polyester forming combinations of hydroxy acids, dicarboxylic acids or derivatives thereof, and diols.
Copolyesters of poly(hydroxyalkanoates) with aromatic dicarboxylic acids and sulfonate functionality are known. For example, Gallagher et al. in U.S. Pat. No. 5,097,004, U.S. Pat. No. 5,171,308, and U.S. Pat. No. 5,219,646; Tietz in U.S. Pat. No. 5,097,005; and Romesser et al. in U.S. Pat. No. 5,295,985 disclose certain sulfonated aromatic copolyesters containing 2 to 40 wt. % of a hydroxy acid component. Warzelhan et al., in U.S. Pat. No. 6,018,004 and U.S. Pat. No. 6,303,677, disclose sulfonated aliphatic-aromatic copolyesters containing hydroxy acids.
Copolyesters of poly(hydroxyalkanoates) with aromatic dicarboxylic acid having sulfonate functionality and poly(alkylene ether) glycol components are also known. For example, Gallagher et al., in U.S. Pat. No. 5,097,004 and U.S. Pat. No. 5,219,646, disclose certain sulfonated aromatic copolyesters containing 2 to 40 wt. % of a hydroxy acid component and a poly(alkylene ether) glycol component.
Some of the known sulfonated aromatic copolyetheresters that contain hydroxyalkanoic acid components have inadequate thermal properties for some applications, as evidenced by the low observed crystalline melting temperatures and glass transition temperatures. The present invention provides sulfonated aromatic copolyetheresters that contain hydroxyalkanoic acids with improved thermal properties, such as crystalline melting points, glass transition temperatures, and heat deflection temperatures, as compared to conventional aromatic copolyetheresters that contain hydroxyalkanoic acids.